1. Field of the Invention
The present invention relates to an analog indication type electronic timepiece and particularly to such an electronic timepiece which can use kinetic energy produced by motions of a user to generate electricity, with which a secondary power source is charged.
2. Description of the Prior Art
The conventional electronic timepieces are driven by an electric energy supplied from a cell. When the cell has been consumed, it must be replaced by a new cell. To avoid such a troublesomeness, an electronic watch including an automated winding generator which is responsive to normal motions of a user's arm for generating an electric energy required to drive the watch has been developed. Attention is now attracted to such a type of electronic timepieces from the viewpoint of reduction of the resources and environmental protection since they do not produce wastes including used cells, in addition to elimination of the troublesome replacement of cells.
Such electronic timepieces comprise an internal power generator for converting a kinetic energy from motions of a user into electric energy which is in turn output from a power generating coil as a charging voltage. The charging voltage is used to charge a secondary power source from which a charged energy is supplied to a timepiece circuit.
If such an electronic timepiece is used to make an analog display, it includes a drive-motor for driving analog indicators, the drive motor being disposed within the case in which the power generator is also contained. This may cause a problem in that the drive motor fails to operate due to magnetic flux produced by the power generating coil of the power generator.
More particularly, watches or the like are frequently constructed such that the power generator is disposed adjacent the drive motor to mount various components within a small case more efficiently. As a relatively large current flows through the power generating coil, part of the magnetic flux thus produced becomes leakage flux which may adversely affect the drive motor, resulting in malfunction of its drive rotor.
Such a problem remarkably appears when a bypass circuit is formed between the power generating coil and the secondary power source to prevent the overcharging to the secondary power source. More particularly, the opposite ends of the power generating coil are shortcircuited by a limiter or the like to halt the charging to the secondary power source as the voltage at the secondary power source exceeds a reference level. At this time, a large shortcircuit current flows through the power generating coil. When drive pulses are given to the drive coil of the drive motor under such a state, the leakage flux from the power generator causes the drive motor to fail, resulting in improper time indication.
Particularly, since an analog indication type electronic timepiece using quartz oscillator is required to be of very high precision, it will be remarkably degraded in commercial value by the aforementioned malfunction in operation.